Synthesis of 4-Epi-L-Rhodosamine Containing Disaccharide

Abstract

Condensation of benzyl 3-azido-2,3,6-trideoxy-α-L-arabino-hexopyranoside (9) with 3,4-di-O-acetyl-2-deoxy-L-fucosyl chloride (10) gave 11. Catalytic hydrogenation of 11 followed by N,N-dimethylation of 12 and deprotection afforded the benzyl glycoside of the title compound, 2-deoxy-L-fucose (1 ? > 4) 4-epi-L-rhodosamine, 14.     

Communication: Synthesis of Polylactosamine Oligomers by Disaccharide Polymerization

Polylactosamine chains, which consist of repeats of the disaccharide βGal(1→4)βGlcNAc(1 →3), are characteristic developmental and tumor associated carbohydrate markers found attached to both glycoproteins and glycolipids.^1,2 In addition to the accumulation of such sequences in a number of diseases, these structures are the immediate biosynthetic precursors to poly-Le^x determinants, {--βGal(1 →4)[αFuc(1 →3)βGlcNAc(1 →3)--)_n, which are recognized also as tumor associated antigens,^3-4 particularly in adenocarcinomas.⁵     

Building Blocks for Glycopeptide Synthesis. Disaccharide Glycosyl Isothiocyanates

Abstract

The reaction of aldose oligosaccharides with aqueous ammonium hydrogencarbonate was revised and optimized for gram scale preparation of glycosylamines, using lactose, cellobiose, maltose, and melibiose as model compounds. The unprotected glycosylamines 1b-4b were transformed into the corresponding hepta-O-acetyl hydrochlorides 1e-4e via diethyl N-glycosylaminomethylenemalonates (1c-4c and 1d-4d). Reaction of le-3e with thiophosgene in a three-phased system led to the target hepta-O-acetylglycosyl isothiocyanates lf-3f in excellent yields. Under the same conditions, the melibiosyl derivative 4e underwent partial hydrolysis to give a mixture of melibiosyl isothiocyanate 4f and the reducing sugar derivative 4h. Treatment of 1f-4f with ammonia resulted in the quantitative formation of N-glycosylthioureas (1g-4g).     

Naphthalene Disaccharide Fragments as Building Blocks for Angucycline Synthesis

ABSTRACT

Methods for the construction of naphthalene oligodeoxy disaccharide fragments, common structural elements of the angucycline antibiotics, are investigated. The triphenylphosphonium bromide- or scandium triflate-catalyzed addition of rhodinal to 4-OH silyl-protected olivoses affords the required 3-O-α-oligodeoxy disaccharides selectively and in high yields.     

Practical Synthesis of 4-Benzylidene-2-phenyl-5(4H)-oxazolones

A simple and alternative method has been developed for the synthesis of 4-benzylidene-2-phenyl-5(4H)-oxazolones via reactions of hippuric acid with various aldehydes in the presence of 2-chloro-4,6-dimethoxy-1,3,5-triazine/N-methylmorpholine at 75 °C.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

Oligonucleotides Containing Disaccharide Nucleosides

Disaccharide nucleosides with 2′‐O‐(D ‐arabinofuranosyl), 2′‐O‐(L ‐arabinofuranosyl), 2′‐O‐(D ‐ribopyranosyl), 2′‐O‐(D ‐erythrofuranosyl), and 2′‐O‐(5‐azido‐5‐deoxy‐D ‐ribofuranosyl) substituents were synthesized. These modified nucleosides were incorporated into oligonucleotides (see Table). Single substitution resulted in a ΔT_m of +0.5 to −1.4° for DNA/RNA and a ΔT_m of −0.8 to −4.7° for DNA/DNA duplexes. These disaccharide nucleosides can be well accommodated in RNA/DNA duplexes, and the presence of a NH₂−C(5″) group has a beneficial effect on duplex stability.     

Practical Synthesis of Sinigrin

Abstract

Sinigrin (1), the most commonly known glucosinolate, is a naturally occurring thiosugar, widely distributed in the botanic family Cruciferae. Sinigrin was first isolated in 1839 from seeds of black mustard in the form of its potassium salt.¹ Commercially available sinigrin is obtained by extraction from horseradish.² So far a number of natural glucosinolates and their analogs have been synthesized.^3-10 The only synthesis of compound 1, leading to a crystalline product on the miligram scale, has been reported by Benn and Ettlinger³ (Scheme 1). Their procedure has been applied by Kjaer and Jensen⁴ for the synthesis of the higher homologue of sinigrin (1), but no information of the overall yield has been provided.     

Practical Synthesis of Menthofuran

A 3-step synthesis of menthofuran from isopulegol in 65–70% is reported.     

Synthesis of the Upstream Terminal Disaccharide of the O-Antigenic Polysaccharide of Vibrio cholerae O37

The terminal disaccharide of the O-antigenic polysaccharide of Vibrio cholerae O37, 4-O-methyl-α-D-QuiNAc-(1→4)-α-d-QuiNAc, was synthesized as methyl glycoside involving glycosylation between glycosyl donor ethyl 2-azido-3-O-benzyl-2,6-dideoxy-4-O-methyl-6-iodo-1-thio-α-d-glucopyranoside and glycosyl acceptor methyl 2-azido-3-O-benzyl-2,6-dideoxy-6-iodo-α-d-glucopyranoside. Dehalogenation, global deprotection, and reduction of the azide to amine were effected in one step by catalytic hydrogenation. It was followed by selective N-acetylation to give the desired deprotected disaccharide.     

Expedient Synthesis of Core Disaccharide Building Blocks from Natural Polysaccharides for Heparan Sulfate Oligosaccharide Assembly

The complex sulfation motifs of heparan sulfate glycosaminoglycans (HS GAGs) play critical roles in many important biological processes. However, an understanding of their specific functions has been hampered by an inability to synthesize large numbers of diverse, yet defined, HS structures. Herein, we describe a new approach to access the four core disaccharides required for HS/heparin oligosaccharide assembly from natural polysaccharides. The use of disaccharides rather than monosaccharides as minimal precursors greatly accelerates the synthesis of HS GAGs, providing key disaccharide and tetrasaccharide intermediates in about half the number of steps compared to traditional strategies. Rapid access to such versatile intermediates will enable the generation of comprehensive libraries of sulfated oligosaccharides for unlocking the “sulfation code” and understanding the roles of specific GAG structures in physiology and disease.     

含有二糖结构的核苷类似物的合成

利用Ferrier重排反应合成了两个系列的连有核音的2,3-不饱和糖苷(其中核耷包括尿苷、腺苷、肌苷等).这些新化合物的结构通过NMR和MS(HRFAB)得到证实.     

Practical Synthesis of Sugar Monophosphonucleotides

A reliable procedure for the preparation of sugar nucleoside monophosphates is presented, which involves condensation of an activated glycosyl‐1‐H‐phosphonate with an appropriately protected nucleoside and simple end‐product isolation via lithium perchlorate–induced precipitation. The utility of these methods is demonstrated by the preparation of a number of purine‐ and pyrimidine‐based sugar nucleoside monophosphate derivatives.     

Practical Synthesis of Aromatic Dithiocarbamates

Oxidation-sensitive N,N-diaryl dithiocarbamates (DTCs) are synthesized in good yields by the generation of metal amide salts from N-benzoyl precursors, followed by addition of CS₂. para-Substituted diphenylamines are prepared by electrophilic aromatic substitution of diphenylbenzamide and saponification. Deacylation of electron-rich species such as bis(p-dimethylaminophenyl)benzamide is challenging because of the oxidative sensitivity of the anionic intermediate but could be achieved in good yield by using n-BuLi to generate a hemiaminal adduct, prior to acidification. The N,N-diaryl DTCs are stable as alkali salts and can be used to produce densely packed monolayers on gold surfaces.     

Practical Synthesis of (+)-Alloisoleucine

Subsequent treatment of N-crotoyl-(1S,2R)-bornane-10,2-sultam with EtMgCl, recrystallization of the product and saponification, afforded R-(-)-3-methylpenthanoic acid which was used for acylation of (1R,2S)-bornane-10,2-sultam. The product was converted into N-[(2S,3R)-2-amino-3-methylpentanoyl]-(1R,2S)-bornane-10,2-sultam by hydroxyamination with 1-chloro-1-nitrosocyclohexane, followed by reduction of the hydroxylamine grouping. Saponification of the sultam imide provided (+)-alloisoleucine.     

Synthesis of Disaccharide Nucleosides by the O‐Glycosylation of Natural Nucleosides with Thioglycoside Donors

Disaccharide nucleosides constitute an important group of naturally‐occurring sugar derivatives. In this study, we report on the synthesis of disaccharide nucleosides by the direct O‐glycosylation of nucleoside acceptors, such as adenosine, guanosine, thymidine, and cytidine, with glycosyl donors. Among the glycosyl donors tested, thioglycosides were found to give the corresponding disaccharide nucleosides in moderate to high chemical yields with the above nucleoside acceptors using p‐toluenesulfenyl chloride (TolSCl) and silver triflate (AgOTf) as promoters. The interaction of these promoters with nucleoside acceptors was examined by ¹H NMR spectroscopic experiments.